Method for reducing center martensitic structure of high-carbon steel coil rod

Abstract

The invention discloses a method for reducing the center martensitic structure of a high-carbon steel coil rod, belonging to the technical field of steel rolling. Microscopic study is performed on the process control and finish rolling control of a heating furnace in a high speed wire rod mill, the cooling process control of air-cooled wire rods, and in particular the cooling process control of the air-cooled wire rods after rolling; in-depth analysis is performed on the transformation process of the center segregated structure of the high-carbon steel from the perspectives of structural transformation thermodynamics and dynamics; a more pertinent quantification operational method is provided for each process link; and the invention is well suited to optimization of the production process of high-carbon steel coil rods in a high speed wire rod mill. By producing 130mm<2> of continuously cast 82B-1 coil rods by the method disclosed by the invention, the martensitic structure in the center of a coil rod is obviously reduced, the aging period of the coil rods is shortened, the plasticity index is obviously improved, and cup and cone fracture and strand breakage of steel wires in the drawing process of a user are notably reduced.

Description

technical field [0001] The invention belongs to the technical field of steel rolling, and in particular provides a method for reducing the martensitic structure in the core of high-carbon steel wire rods, which is suitable for high-speed wire factories to produce hot-rolled wire rods for high-carbon steel drawing, and is used to reduce the The martensitic structure in the core of hot-rolled wire rod caused by segregation of components in the center of the slab. Background technique [0002] The core segregation structure of high-carbon steel wire rod has always been a problem that plagues the deep processing industry, especially the strand industry. The impact is the greatest, resulting in cup-cone fractures during the drawing process of the steel strands, and the torsion index of the steel wires is significantly reduced, resulting in broken wires during the stranding process, resulting in reduced production efficiency and increased costs. The fundamental reason is that the...

AI Technical Summary

Problems solved by technology

[0003] The previous research on the segregation structure of the core of high carbon steel also introduced the continuous casting process, steel rolling and air cooling process, but for the control process of the high-speed wire plant is relatively extensive, and the setting of some parameters also lacks technical data support, guidance Sex is not strong

Patent 200810231435.1 proposes a method for shortening the aging time of high-carbon steel, in which some introductions are made to the rolling and cooling process, but the rolling process adopts the rolling process of finishing rolling + reducing and sizing, which requires a large investment in equipment and complicated processes. On the other hand, some measures have been proposed in the air-cooling process, such as adopting weak cooling in the later stage of phase transformation, reducing the opening of the fan and adding a heat preservation cover, but there is no effect on cooling. The rate, the temperature of entering and exiting the insulation cover, and the holding time provide targeted data, which is difficult to perform actual quantitative operations on site

Patent 200910169807.7 also proposes a production method of high carbon steel wire rod, which defines the rolling start temperature and spinning temperature, and explains the fan settings of the air-cooled line before phase change and in the early stage of phase change, but does not take into account seasonal changes and ambient temperature fluctuations on the process, there is no specific basis for temperature setting in terms of on-site flexible operation

Patent 200410155450.4 proposes a more detailed high-carbon steel wire rod production process, which is very suitable for steel mills and rolling mills to produce high-performance high-carbon steel wire rods. There is no more detailed description on the control of segregation organization

Patent 200410155451.9 proposes a forced cooling process for 82B hot-rolled wire rods for strands after rolling, which is very suitable for high-strength strands in high-strength wire factories. The length of the cold line is too short to achieve effective control of the segregated structure in the core of the rod, so no further explanation is given on this

Patent 200910088147.X proposes a method to reduce the difference between the center and side structures of large-scale high-carbon steel wire rods. By increasing the alloy composition Cr to improve the hardenability of the wire rod, combined with the strong cooling before 510°C after rolling, Increase the sorbite rate in the core of the wire rod, but it is difficult to reduce the martensitic structure in the core of the wire rod even if slow cooling is adopted after 510°C

Baosteel Technology introduced the method of reducing martensite in the core of 82B wire rod in the article "Practice and Thinking of Production of SWRH82B High Carbon Steel Wire Rod with Vanadium Added by Electric Furnace Continuous Casting", but Baosteel's high-speed line adopts finishing rolling + reducing sizing Process method, in addition, in the aspect of air cooling line control, adjust the cooling control process of the high-end branch factory, from the spinning temperature of 880-900 ℃ to 920 ℃, 820 ℃, the air volume of the fan is adjusted from 90% of the 1# to 10# fan Various schemes such as 75%, 50%, 25% and the combination of fast and slow cooling have greatly reduced the content of martensitic structure in the core, but there has never been an explanation of the temperature control points of the air-cooled line, which lacks practical operability on site

Iron and Steel introduced the causes of center segregation in detail in the article "Control of Center Segregation of High Carbon Steel Wire Rod". , in actual production, the temperature control and cooling rate of the air-cooled line are not a constant, and careful research and analysis are needed on the temperature control process in different tissue transformation stages

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